title: Inhibition of NADPH-cytochrome P450 reductase by tannic acid in rat liver microsomes and primary hepatocytes: methodological artifacts and application to ischemia-reperfusion injury.
abstract: Tannic acid (TA) inhibits nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome P450 reductase (CPR) activity, which is measured by reduction of cytochrome c, in rat liver microsomes (RLMs). In the current study, we noticed that TA directly reduces cytochrome c in the absence of microsomes, thus confounding the CPR activity assay. A method is presented that measures CPR activity in the presence of TA by subtracting the cytochrome c reduction in the absence of NADPH (TA effect) from that in the presence of NADPH (TA plus CPR effect). The method was used to determine the inhibitory effect of TA in RLMs, recombinant CPR enzyme, and primary hepatocytes. Additionally, application of TA in a study of role of CPR in a primary rat hepatocyte model of ischemia-reperfusion (IR) was investigated. TA showed concentration-dependent, complete inhibition of CPR with half maximal inhibitory concentration (IC(50) ) values of 58.2 μM in RLMs and 54.6 and 275 μM in primary rat hepatocytes in the absence and presence of serum in the medium, respectively. Additionally, inhibition of CPR by TA was associated with a significant reduction in reactive oxygen species and cell death after IR injury. These data may be useful in future studies using TA as an inhibitor of CPR in microsomes and primary hepatocytes.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106.
authors.forename: Venkateswaran C
authors.initials: VC
authors.lastname: Pillai
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106. Electronic address: reza.mehvar@ttuhsc.edu.
authors.forename: Reza
authors.initials: R
authors.lastname: Mehvar
mesh_terms: D000818:Animals; D016477:Artifacts; D001681:Biological Assay / Q000379:methods; D015687:Cell Hypoxia / Q000187:drug effects; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D009251:NADPH-Ferrihemoprotein Reductase / Q000037:antagonists & inhibitors*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D015427:Reperfusion Injury / Q000201:enzymology* / Q000378:metabolism; D013634:Tannins / Q000494:pharmacology*
chemical_list: D016895:Culture Media, Serum-Free; D017382:Reactive Oxygen Species; D013634:Tannins; D045304:Cytochromes c; D009251:NADPH-Ferrihemoprotein Reductase